C4.4 (Mech) Industrial Engine Cooling System - Test Caterpillar


Cooling System - Test
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1.1. Test Tools For The Cooling System
2.1. Checking the Filler Cap
3.1. Testing The Radiator And Cooling System For Leaks

Remember that temperature and pressure work together. When a diagnosis is made of a cooling system problem, temperature and pressure must be checked. Cooling system pressure will have an effect on the cooling system temperature. For an example, refer to Illustration 1. This will show the effect of pressure on the boiling point (steam) of water. This will also show the effect of height above sea level.



Illustration 1g00286266
Cooling system pressure at specific altitudes and boiling points of water

------ WARNING! ------

Personal injury can result from hot coolant, steam and alkali.

At operating temperature, engine coolant is hot and under pressure. The radiator and all lines to heaters or the engine contain hot coolant or steam. Any contact can cause severe burns.

Remove filler cap slowly to relieve pressure only when engine is stopped and radiator cap is cool enough to touch with your bare hand.


The coolant level must be to the correct level in order to check the coolant system. The engine must be cold and the engine must not be running.

After the engine is cool, loosen the pressure cap in order to relieve the pressure out of the cooling system. Then remove the pressure cap.

The level of the coolant should not be more than 13 mm (0.5 inch) from the bottom of the filler pipe. If the cooling system is equipped with a sight glass, the coolant should be to the proper level in the sight glass.

Test Tools For The Cooling System

Table 1
Required Tools 
Part Number  Part Name  Qty 
4C-6500  Digital Thermometer 
8T-2700  Blowby/Air Flow Indicator 
9U-7400  Multitach Tool Group 
9S-8140  Pressurizing Pump 

------ WARNING! ------

Making contact with a running engine can cause burns from hot parts and can cause injury from rotating parts.

When working on an engine that is running, avoid contact with hot parts and rotating parts.




Illustration 2g00876179
4C-6500 Digital Thermometer

The 4C-6500 Digital Thermometer is used in the diagnosis of problems that cause overheating or overcooling in the engine. This tool can be used to check the temperature in several areas of the cooling system. The testing procedure is in Tool Operating Manual, NEHS0554.



Illustration 3g00313263
8T-2700 Blowby/Air Flow Indicator

The 8T-2700 Blowby/Air Flow Indicator is used to check the air flow through the radiator core. Refer to Special Instruction, SEHS8712, "Using the 8T-2700 Blowby/Air Flow Indicator" for the test procedure for checking blowby and air flow.



Illustration 4g00286276
9U-7400 Multitach Tool Group

The 9U-7400 Multitach Tool Group is used to measure the fan speed. Refer to Operating Manual, NEHS0605, " 9U-7400 Multitach Tool Group" for the testing procedure.



Illustration 5g00286369
9S-8140 Pressurizing Pump

The 9S-8140 Pressurizing Pump is used to test the filler caps. This pressurizing pump is also used to pressure test the cooling system for leaks.

Checking the Filler Cap

Table 2
Required Tools 
Part Number  Part Name  Qty 
9S-8140  Pressurizing Pump 

One cause for a pressure loss in the cooling system can be a faulty seal on the radiator pressure cap.



Illustration 6g00296067
Typical schematic of filler cap
(1) Sealing surface between the pressure cap and the radiator

------ WARNING! ------

Personal injury can result from hot coolant, steam and alkali.

At operating temperature, engine coolant is hot and under pressure. The radiator and all lines to heaters or the engine contain hot coolant or steam. Any contact can cause severe burns.

Remove filler cap slowly to relieve pressure only when engine is stopped and radiator cap is cool enough to touch with your bare hand.


To check for the amount of pressure that opens the filler cap, use the following procedure:

  1. After the engine cools, carefully loosen the filler cap. Slowly release the pressure from the cooling system. Then, remove the filler cap.

  2. Inspect the pressure cap carefully. Look for damage to the seal. Look for damage to the surface that seals. Remove any debris on the cap, the seal, or the sealing surface.

    Carefully inspect the filler cap. Look for any damage to the seals and to the sealing surface. Inspect the following components for any foreign substances:

    • Filler cap

    • Seal

    • Surface for seal

    Remove any deposits that are found on these items, and remove any material that is found on these items.

  3. Install the pressure cap on the 9S-8140 Pressurizing Pump.

  4. Observe the exact pressure that opens the filler cap.

  5. Compare the pressure to the pressure rating that is found on the top of the filler cap.

  6. If the filler cap is damaged, replace the filler cap.

Testing The Radiator And Cooling System For Leaks

Table 3
Required Tools 
Part Number  Part Name  Qty 
9S-8140  Pressurizing Pump 

Use the following procedure to test the radiator and the cooling system for leaks.

------ WARNING! ------

Personal injury can result from hot coolant, steam and alkali.

At operating temperature, engine coolant is hot and under pressure. The radiator and all lines to heaters or the engine contain hot coolant or steam. Any contact can cause severe burns.

Remove filler cap slowly to relieve pressure only when engine is stopped and radiator cap is cool enough to touch with your bare hand.


  1. When the engine has cooled, loosen the filler cap to the first stop. Allow the pressure to release from the cooling system. Then remove the filler cap.

  2. Make sure that the coolant covers the top of the radiator core.

  3. Put the 9S-8140 Pressurizing Pump onto the radiator.

  4. Use the pressurizing pump to increase the pressure to an amount of 20 kPa (3 psi) more than the operating pressure of the filler cap.

  5. Check the radiator for leakage on the outside.

  6. Check all connections and hoses of the cooling system for leaks.

    The radiator and the cooling system do not have leakage if all of the following conditions exist:

    • You do NOT observe any leakage after five minutes.

    • The dial indicator remains constant beyond five minutes.

    The inside of the cooling system has leakage only if the following conditions exist:

    • The reading on the gauge goes down.

    • You do NOT observe any outside leakage.

    Make any repairs, as required.

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